This invention relates generally to sound sensing devices with microphone booms, and more particularly to headsets that utilize a movable boom and an acoustic valve to enable multiple operating modes with different boom lengths.
Communications headsets can be used in a diversity of applications, and are particularly effective for use with mobile communications devices such as cellular telephones. Some headsets have long booms which place the acoustic sensing point near the user""s mouth, while other headsets have short booms or no booms at all. The term xe2x80x9cacoustic sensing pointxe2x80x9d is used herein to refer to the point (or more generally, location) in space where a headset collects sound waves. In some telephone headsets, the microphone is located directly at the acoustic sensing point at the distal end of a boom. In others, the boom is a hollow tube, and the sound travels from the sound sensing point at the distal end of the boom to the microphone located near the proximal end of the boom. When a short boom or boomless headset is used, there is a large distance between the user""s mouth and the acoustic sensing point of the headset. When such headsets are used in noisy environments, this typically leads to a lower than desirable signal-to-noise ratio in the transmit signals (i.e. ratio between the amount of signals associated with the desired acoustic source such as the user""s mouth and those from background noise). However, because of the unobtrusive and stylish appearance and easy stowability of compact short boom or boomless headsets, users continue to demand these types of headsets in many applications.
As a compromise between the needs for compactness and style and for satisfactory transmit signal quality, communications headsets with foldable booms are available. Some of these headsets have a non-operational compact mode, with the boom folded on top of the body, that allows for stowability, and also an extended-boom mode in which the headset can operate with adequate transmit signal quality. Hence, a user can stow a foldable communications headset in the compact mode, and in the extended-boom mode the headset can be used for communication.
Conventional headsets with foldable booms do not offer different operating modes. When the compact mode is chosen, these headsets are inoperable. This is because, with conventional headsets, when the boom is folded to place the headset in the compact mode, the acoustic sensing point typically ends up behind the user""s ear, where it is too far from the user""s mouth to assure a sufficient transmit signal level and signal-to-noise ratio at normal speech levels.
Furthermore, national and international telecommunications standards have been established, and in some places legislated, that define acceptable Send Loudness Ratings (SLR) that a telephone device must provide in order to be compatible with the telephone network in their jurisdiction. At present, a telephone device with a handset or headset can meet such compatibility requirements only if the acoustic sensing point is located within a limited range of user-adjustable distances from the user""s mouth, which means that telephone headsets with foldable booms having a large range of movement cannot operate in both in the folded-boom and the compact modes.
Accordingly, it is desirable to provide a communications headset that operates in multiple modes, including at least a compact mode and an extended-boom mode, with high signal-to-noise ratios in the various modes. Additionally, what is desired is a reliable mechanism that enables the headset to maintain a transmit signal level that is consistent with the speech level in different modes of operation.
The present invention overcomes the limitations of conventional adjustable communications headset design by allowing the selection among multiple locations to receive acoustic input in response to the position of an adjustable boom. In one embodiment, the boom is adjustable into various positions and, with each position, enables the acoustic coupling of the microphone with one of a plurality of openings on the boom or the main body, whereby only the acoustically coupled opening functions as the acoustic sensing point.
According to one aspect of the present invention, when the boom changes position, the locations of one or more openings on the boom relative to the desired acoustic source are also changed. The opening that can most favorably be used as the acoustic sensing point is acoustically coupled to the microphone. Hence, in a preferred embodiment of the present invention, the acoustic sensing point is located at the opening on the boom which is closest to the desired acoustic source given the boom""s position. In another embodiment, the boom has a sliding or pivoting secondary segment that can extend the boom to move the acoustic sensing point even closer to the desired acoustic source.
According to another aspect of the present invention, the movement of an adjustable boom operates an acoustic valve that couples the microphone to the acoustic sensing point, which may be located at any one of a plurality of locations on the boom or the main body given the boom""s position. The boom may rotate about a pivot or slide along an axis. In one embodiment that takes advantage of this aspect of the present invention, the boom can be positioned in at least a first and a second position, and the headset has at least a first and a second openings. When the boom is in the first position, the first opening is closer to the desired acoustic source than the second opening, and, accordingly, the valve couples the microphone to the first opening. Conversely, when the boom is in the second position, the second opening is closer to the desired acoustic source, and the valve couples the microphone to the second opening.
The movable boom also enables the implementation of control mechanisms in the communications headset to compensate for different levels of sound input in different operating modes based on the different positioning of the boom. In one embodiment, the headset can include a transmit controller for adjusting the transmit gain in the electrical signals in response to the boom""s position. In another embodiment, the communications headset can adjust the sensitivity of the microphone to received acoustic signals by altering the total volume of all acoustic cavities to which the microphone is exposed to, again based on the boom""s position. In yet another embodiment, the boom includes acoustic channels that are designed to have different levels of acoustic energy attenuation. A further advantage of this aspect of the present invention is that the background noise can be effectively masked if the overall transmission level of the communications headset is reduced when it is operating with a high signal-to-noise ratio.
Additional advantages of the invention will be set forth in part in the description which follows and in part will be apparent from the description or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims and equivalents.